Alignment ferrule assemblies and connectors for evanescent optical couplers and evanescent optical couplers using same

ABSTRACT

Disclosed is an optical interconnection device that includes an alignment ferrule assembly formed from an alignment substrate and optical fibers. The optical interconnection device also has an alignment assembly formed by a planar support member with guide features. A receiving region resides between the guide features in which the alignment substrate is secured. An evanescent optical coupler can be formed using the optical interconnection device as a first device and another optical interconnection device as a second device. The second device is constituted by a planar lightwave circuit that operably supports waveguides and an adapter. The adapter of the second device is configured to engage the alignment assembly of the first device to place the optical fibers and the optical waveguides of the respective devices in evanescent optical communication.

FIELD

The present disclosure generally relates to optical couplers used toperform optical coupling between fibers and planar lightwave circuit(PLC) waveguides, and more particularly relates to ferrules assembliesand connectors for evanescent optical couplers for optically couplingoptical fibers to waveguides of PLCs, and to evanescent optical couplersusing the ferrule assemblies and connectors.

BACKGROUND

Optical interconnects based on ion-exchanged (IOX) PLC waveguidesrealized in thin glass substrates are a promising alternative toelectrical (e.g. copper), or optical-fiber-based high-density, highbit-rate, short distance (less than 1 m) links for high-performancecomputing and data center applications. Such IOX PLC waveguides have theadvantage of dense routing, flexibility, integration, and co-packagingwith electronic integrated circuits. Other PLC technologies based on,for example Si, InP, and GaN materials, provide light sources,detectors, and/or modulators essential for implementation ofoptoelectronic transceivers.

A high bit-rate optical signal is typically delivered to PLC waveguidesthrough an optical fiber. Thus, a low-cost, low-loss connectivitysolution from a single mode fiber to an PLC waveguide is desirable. Astandard approach is to use an end-to-end coupling (also called edgecoupling or butt coupling) between the single mode fiber and the PLCwaveguide. Such coupling requires that the PLC substrate edge and thefiber end be processed to achieve an optical quality (i.e., smoothlypolished) surface for low-loss coupling. This coupling also requiresthat mode sizes (i.e., mode-field diameters) of the guided mode of thefiber and the guided mode of the PLC waveguide be closely matched.

An alternative approach to end-to-end coupling is to use evanescentcoupling between the fiber and the PLC waveguide. Unfortunately,efficient evanescent optical coupling between a fiber and an PLCwaveguide requires that the separation as well as the alignment betweenthe fiber and the PLC waveguide be controlled to challenging tolerances,e.g., to micron or even sub-micron levels. While evanescent couplingdoes not require precise matching of the fiber and PLC waveguide modesshapes for low loss coupling, it does require matching propagationconstants of the fiber and PLC waveguide guided waves. In evanescentcoupling, the optical power transfer mechanism occurs all along aninterface that is typically parallel to the direction of the travel ofthe guided mode, as opposed to end-to-end coupling where the powertransfer occurs abruptly at an interface perpendicular to the directionof travel of the guided mode.

Evanescent optical couplers used to optically couple optical fibers toPLC waveguides of a PLC require both coarse and fine alignment to obtainhigh coupling efficiency (i.e., a low-loss connection) between thefibers and the PLC waveguides. In addition, it is advantageous that theconnectors used to form the evanescent optical coupler can be readilyconnected and disconnected.

SUMMARY

An embodiment of the disclosure is directed to an opticalinterconnection device for establishing evanescent optical couplingbetween optical fibers and optical waveguides of a photonic lightwavecircuit (PLC). The device comprises: a) an alignment ferrule assemblycomprising: i) an alignment substrate having a front-end section with afront end, a top surface, a bottom surface and a substrate central axis;ii) an array of optical fibers, with each optical fiber having a fibercentral axis and an end section with a glass portion defined by glasscore, a glass inner cladding and a glass-portion surface that residesimmediately adjacent the glass core, and wherein the end sections of theoptical fibers are secured to the bottom surface of the alignmentsubstrate with the glass-portion surfaces facing away from the bottomsurface of the alignment substrate and with the fiber central axesaligned with the substrate central axis; and b) an alignment assemblycomprising: a planar support member having a back-end section with aback end, a top surface and a bottom surface, first and secondspaced-apart guide-feature support members that downwardly depend fromthe bottom surface of the planar support member and that respectivelysupport first guide features; and a receiving region between the firstand second guide features in which the alignment substrate of thealignment ferrule assembly is secured.

Another embodiment of the disclosure an evanescent optical couplercomprising: the optical interconnection device as described immediatelyabove as a first optical interconnection device; a second opticalinterconnection device comprising: a planar lightwave circuit (PLC) thatoperably supports PLC optical waveguides; and an adapter operablysupported by the PLC; and wherein the adapter is configured to matinglyengage the alignment assembly of the first optical interconnectiondevice to place the optical fibers and the optical waveguides inevanescent optical communication.

Another embodiment of the disclosure is an optical interconnectiondevice for establishing evanescent optical coupling between an array ofoptical waveguides and an array of optical fibers. The device comprises:a PLC having a surface and that supports the array of opticalwaveguides, wherein the array has first and second sides; an adapterhaving an interior, spaced apart first and second tabs and spaced apartfirst and second arms each having a first guide feature, wherein thefirst and second tabs of the adapter are attached to the surface of thePLC adjacent and outboard of the first and second sides of the array ofwaveguides; a stop fixture comprising a recess with an inside edge, thestop fixture attached to the surface of the PLC and within the interiorof the adapter and relative to the optical waveguide array, with therecess defining an alignment surface.

Another embodiment of the disclosure is an evanescent optical coupler,comprising: the optical interconnection device as described immediatelyabove as a first optical interconnection device; a second opticalinterconnection device comprising: an alignment ferrule assemblycomprising an alignment substrate having a substrate central axis andthat supports an array of optical fibers; an alignment assembly thatoperably supports the alignment ferrule assembly; and wherein theadapter is configured to matingly engage with the alignment assembly ofthe second optical interconnection device to place the optical fibersand the optical waveguides in evanescent optical communication.

Another embodiment of the disclosure is a method of forming an alignmentferrule assembly. The method comprises: drawing a glass preform to forma long glass member having a longitudinal axis, wherein the glasspreform has at least one perform precision feature that defines at leastone long glass member precision feature; cutting the long glass memberin a direction substantially perpendicular to the longitudinal axis toform an alignment substrate having at least one substrate precisionfeature defined by the at least one long glass sheet precision featureand further comprising a planar surface; and securing a plurality ofoptical fibers to the planar surface.

Another embodiment of the disclosure is a method of forming alignmentferrule assembly. The method comprises: securing a plurality of opticalfibers to a bottom surface of a planar alignment substrate so that theoptical fibers run substantially parallel to the substrate axis and havea pitch P, wherein the planar alignment substrate has one or more edges;and forming at least one alignment bump on at least one of the edges.

Another embodiment of the disclosure is a method of forming a firstoptical interconnection device configured to receive a second opticalinterconnection device having an alignment ferrule assembly thatsupports an array of optical fibers having a pitch P, comprising:providing a planar lightwave circuit (PLC) comprising a PLC substratehaving a planar surface and that supports an array of PLC waveguideshaving the pitch P; and securing a stop fixture to the planar surfaceand relative to the array of PLC waveguides so that the array of opticalfibers and the array of PLC optical waveguides are operably aligned whenthe alignment ferrule assembly contacts the stop fixture.

Additional features and advantages will be set forth in the detaileddescription which follows, and, in part, will be apparent to thoseskilled in the art from that description or recognized by practicing theembodiments as described herein, including the detailed descriptionwhich follows the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are merely exemplary and are intendedto provide an overview or framework to understanding the nature andcharacter of the claims. The accompanying drawings are included toprovide a further understanding, and are incorporated in and constitutea part of this specification. The drawings illustrate one or moreembodiments, and together with the description explain the principlesand operation of the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are cross-sectional views of two example polymer-cladD-shaped optical fibers (“fibers”) used to form the evanescent opticalcouplers disclosed herein.

FIGS. 2A and 2B are side views of an end section of the example fiber ofFIG. 1B that shows a stripped end portion of an example fiber used toform the evanescent optical coupler disclosed herein.

FIG. 2C is a back elevated view of the end section of the example fiberof FIGS. 2A and 2B.

FIG. 2D is a cross-sectional view of an example glass portion of anexample optical fiber, wherein the glass portion includes protrusionsthat define longitudinal recess that are useful for channelingcontaminants away from where evanescent coupling with the core takesplace when the fiber is interfaces with a PLC waveguide.

FIG. 3A is a top elevated and partially exploded view and FIG. 3B is atop elevated assembled view of an example alignment assembly asdisclosed herein.

FIGS. 4A and 4B are similar to FIG. 3B and shows the alignment assemblywith a latch member.

FIG. 5A is a top elevated view that shows the alignment assembly of FIG.4B operably disposed above an alignment ferrule assembly in preparationto form the plug connector, while FIG. 5B shows the assembled plugconnector.

FIG. 6A is a top elevated partially exploded view and FIG. 6B isassembled view of an example PLC.

FIG. 6C is a close-up cross-sectional view of the PLC substrate of thePLC showing the core of the PLC waveguide and the cladding of the PLCwaveguide as defined by the portion of the PLC substrate immediatelysurrounding the PLC waveguide core.

FIG. 7A is top-elevated partially exploded view and FIG. 7B is anassembled view of the PLC of FIG. 6B along with a receptacle adapterthat together define a receptacle connector configured to matinglyengage with the plug connector of FIG. 5B to define an evanescentoptical coupler.

FIG. 8A shows the receptacle connector of FIG. 7B along with the plugconnector arranged in position to operably engage the receptacleconnector to form an evanescent optical coupler.

FIG. 8B is the same as FIG. 8A but shows the assembled evanescentoptical coupler.

FIG. 8C is a cross-sectional view in the y-z plane of a simplifiedversion of the evanescent optical coupler of FIG. 8B.

FIG. 9 is similar to FIG. 8B and shows the latch member in its latchingposition.

FIGS. 10A through 10G are cross-sectional views of example evanescentoptical couplers illustrating different configurations for generating apressing force for pressing the fibers and PLC waveguides together inthe evanescent coupling region.

FIG. 11A is a partially exploded bottom view and FIG. 11B is anassembled bottom view of an example alignment ferrule assembly asdisclosed herein.

FIG. 11C is a top-elevated view of the assembled alignment ferruleassembly of FIG. 11B.

FIG. 11D is a cross-sectional view of an example alignment ferruleassembly wherein the alignment substrate acts as a shaping member thatshapes the fibers so that the end sections of the fibers are flat on thebottom side of the alignment substrate extend at an angle from the backof the alignment substrate.

FIG. 12A is a top-down view of an example PLC and FIG. 12B is an x-ycross-sectional view of the example PLC of FIG. 12A as taken at the lineB-B in FIG. 12A.

FIG. 13A is a cross-sectional view of the alignment ferrule assembly ofFIG. 21C along with the example PLC of FIG. 12B.

FIG. 13B is a top-down view of the alignment ferrule assembly and PLC ofFIG. 13A illustrating how the alignment ferrule assembly is used toalign the fibers with the PLC waveguides.

FIGS. 14A and 14B are cross-sectional views of an example ferruleassembly wherein the glass portion of each fiber has a keyholecross-sectional shape.

FIG. 15 is a cross-sectional view of an example alignment ferruleassembly engaged with an example PLC, with a bump on the edge of thealignment substrate contacting a stop fixture of the PLC to define aselect alignment offset.

FIG. 16 is a schematic diagram of an example bump-forming apparatus forforming alignment bumps.

FIG. 17 is similar to FIG. 13B and shows example configuration thatemploys three alignment bumps on the alignment substrate.

FIG. 18A is a schematic diagram of a drawing system used to form glasssheets or long glass members from a preform.

FIG. 18B is a top elevated view of an example alignment substrate thathas been cut from a glass sheet formed using the drawing system of FIG.18A.

FIG. 19 is similar to FIG. 15 and shows an example alignment ferruleassembly wherein the alignment substrate has been formed from a drawnglass sheet similar to that shown in FIG. 18B, and wherein the alignmentsubstrate includes a V-groove sized to receive a V-shaped alignmentsurface of the glass portion of the fiber.

FIG. 20 is similar to FIG. 18B and an example of a glass sheet having anangled edge.

FIG. 21A is a top elevated and partially exploded view of an examplealignment ferrule assembly formed using the alignment substrate of FIG.20.

FIG. 21B shows the example alignment ferrule assembly of FIG. 21Aoperably arranged above an example PLC.

FIG. 21C shows the assembled structure of FIG. 21B.

FIG. 22 is a bottom-up view of the example alignment substrate andfibers used to form the example alignment ferrule assembly, with thetips of the fibers residing at the transition between the front-endsection and the back-end section.

FIG. 23 shows an example drawn long glass member used to form V-shapedalignment substrates such as shown in FIG. 22.

FIGS. 24A and 24B are top-down views of an example PLC similar to thatshown in FIG. 12A and that includes an example stop fixture with aV-shaped recess sized to closely accommodate the V-shaped front-endsection of the alignment substrate of the alignment ferrule assembly ofFIG. 22.

FIG. 24C is similar to FIG. 24B and shows the alignment substrate havingthree alignment bumps formed at different positions along the edge ofthe alignment substrate.

FIG. 25A is similar to FIG. 23 and illustrates an example of how thelong glass member can be cut so that the alignment substrate has anglededges.

FIG. 25B is similar to FIG. 22 and shows an example alignment ferruleassembly that employs the alignment substrate of FIG. 25A.

FIG. 25C is a close-up y-z cross-sectional view of the alignmentsubstrate of FIG. 25A showing an angled edge that makes the top surfaceof the alignment substrate have a smaller area than the bottom surfaceof the alignment substrate.

FIG. 26A is top-down view of an example PLC wherein the stop fixture hasan angle edge configured to accommodate the angled edge of the alignmentsubstrate of the alignment ferrule assembly of FIG. 25B.

FIG. 26B is similar to FIG. 26A and also shows the alignment ferruleassembly of FIG. 25B.

FIG. 26C is a close-up y-z cross-sectional view that shows thecomplementary wedge angles of the stop fixture and the alignmentsubstrate.

FIG. 26D is similar to FIG. 26C and illustrates an example where thewedge angles are not the same so that there is a line of contact betweenthe stop fixture of the PLC and the alignment substrate of the alignmentferrule assembly.

FIG. 27A is similar to FIG. 25A and shows an example cross-sectionalshape having triangular protrusions at the back end that assist inproviding a pressing force at the evanescent coupling region.

FIG. 27B is a top-down view of an example alignment ferrule assemblythat utilizes the alignment substrate formed from the long glass memberof FIG. 27A.

FIG. 28 is similar to FIG. 26B but with the alignment ferrule assemblyof FIG. 27B.

FIGS. 29A through 29E are top-down views that illustrate alternateembodiments (configurations) for the alignment substrate of thealignment ferrule assembly and the stop fixture of the PLC.

FIGS. 30A through 30D are top-down views of alignment ferrule assemblieswherein the alignment substrate includes spaced-apart holes sized toengage corresponding posts of the stop fixture.

FIGS. 31A and 31B are a top elevated views of an example long glassmember used to form stop fixtures having a V-groove recess.

FIG. 32 is a top-elevated view that shows how the stop fixture with theV-shaped recess aligns the alignment ferrule assembly to PLC waveguidesby closely receiving the V-shaped front end of the alignment substrate.

FIG. 33A is a top elevated view of an example alignment ferrule assemblyshown disposed beneath an example alignment assembly that utilizesalignment tubes.

FIG. 33B shows the assembled plug connector of FIG. 33A.

FIG. 34A is a side view of the example alignment ferrule assemblysimilar to that of FIG. 11D along with the example plug connector ofFIG. 33B in the process of forming a plug connector.

FIG. 34B shows the resulting plug connector formed by interfacing thealignment assembly and alignment ferrule assembly of FIG. 34A.

FIG. 35A is a side view of the plug connector of FIG. 34B in positionrelative to an example PLC to form an evanescent optical coupler,wherein the PLC includes an example receptacle assembly that utilizesalignment tubes.

FIG. 35B shows the evanescent optical coupler formed by operablyengaging the plug connector and the PLC of FIG. 35A.

FIGS. 36A and 36B are top elevated views of an example plug connectorand receptacle connector respectively having a tube-based alignmentassembly and a tube-based receptacle assembly, illustrating theformation of an example evanescent optical coupler by matingly engagingthe plug and receptacle connectors.

DETAILED DESCRIPTION

Reference will now be made in detail to the present embodiments,examples of which are illustrated in the accompanying drawings. Wheneverpossible, the same reference numerals will be used throughout thedrawings to refer to the same or like parts.

Cartesian coordinates are used in some of the Figures for reference andare not intended to be limiting as to direction or orientation.

For purposes of description herein, the terms “upper,” “lower,” “right,”“left,” “rear,” “front,” “vertical,” “horizontal,” “top,” “bottom,”“side,” and derivatives thereof, shall relate to the disclosure asoriented with respect to the Cartesian coordinates in the correspondingFigure, unless stated otherwise. However, it is to be understood thatthe disclosure may assume various alternative orientations, except whereexpressly specified to the contrary.

The term “mode” is short for “guided mode,” which describes an allowedspatial distribution of light that propagates in a waveguide, whether itbe an optical fiber or substrate-based PLC waveguide. A mode can have atransverse electric (TE) polarization or a transverse magnetic (TM)polarization. A single mode PLC waveguide supports only one TE and oneTM mode. Modes are identified by a mode number m, where m=0 is thefundamental mode andm=1, 2, 3, . . . are higher-order modes.

The abbreviation “nm” stands for “nanometer,” which is 1×10⁻⁹ meter.

The abbreviation “μm” stands for “micron” or “micrometer,” which is1×10⁻⁹ meter.

It is also to be understood that the specific devices and processesillustrated in the attached drawings, and described in the followingspecification, are simply exemplary embodiments of the inventiveconcepts defined in the appended claims. Hence, specific dimensions andother physical characteristics relating to the embodiments disclosedherein are not to be considered as limiting unless the claims expresslystate otherwise. Additionally, embodiments depicted in the figures maynot be to scale or may incorporate features of more than one embodiment.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itself,or any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

The term “comprises” as used herein, such as in the phrase “A comprisesB,” is intended to include as a special case “A consists of B.”

The terms “plug connector” and “receptacle connector” are used below forconvenience to discern between male and female optical interconnectiondevices used to establish evanescent optical coupling (i.e., evanescentoptical communication) between fibers and PLC waveguides. The term“connector” is used herein as shorthand for “optical interconnectiondevice.” Thus, a plug connector can be referred to as a first opticalinterconnection device or a plug optical interconnection device while areceptacle connector can be referred to as a second opticalinterconnection device or a receptacle optical interconnection device.

Example Polymer-Clad Fibers

FIGS. 1A and 1B are cross-sectional views of two example polymer-cladoptical fibers (“fiber”) 10. The fiber 10 includes a central axis AC andhas an overall diameter DF. The fiber 10 includes a glass portion 16defined by a glass core 18 of refractive index n_(co) and a glass innercladding 54 of refractive index n_(cl), where n_(co)>n_(cl).

The fiber 10 is a preferably a single mode fiber. In an example, thefiber 10 can be a small diameter few-moded fiber, such as a fiber thatis designed to support only a few guided modes. In the examples below,the fiber 10 is assumed to be single mode unless otherwise stated. Atypical single mode fiber can have a core refractive index n_(co) of1.4491 and a cladding refractive index n_(cl) of 1.444 at a wavelengthof 1550 nm. Thus, a typical range on the effective index N_(F) of aconventional single mode fiber is 1.444<N_(F)<1.4491. However, asdiscussed below, the fiber 10 disclosed herein has substantially highercore and cladding refractive indices n_(co) and n_(cl) obtained forexample via updoping of the core and cladding glass material.

The fiber 10 includes an outer cladding 58 positioned around the glassportion 16 and in particular around the glass inner cladding 54. Theouter cladding 58 is made of a polymer and so is referred to hereinafteras the polymeric outer cladding 58 to distinguish from the glass innercladding 54. The combination of the glass core 18, the glass innercladding 54 and the polymeric outer cladding 58 is what makes the fiber10 a polymer-clad optical fiber.

The polymeric outer cladding 58 can be composed of two parts: an inner,softer layer and an outer harder layer. The polymeric material thatmakes up the polymeric outer cladding 58 may include high densityacrylate, low density acrylate, polyethylene, polystyrene,polymethylmethacrylate, nylon, silicone, silicone based materials,fluorinated acrylates, polyimide, ethylene tetrafluoroethylene,fluoroacrylate, fluoromethacrylate and combinations thereof. Thepolymeric material may be optically transparent. The polymeric outercladding 58 may have a diameter ranging from between about 10 μm andabout 900 μm, between about 80 μm and about 250 μm or between about 100μm and 150 μm.

The glass inner cladding 54 and the polymeric outer cladding 58cooperate to form a cladding 22 disposed around the core 18. The fiber10 has an outer surface 24, which can be defined either by: i) thepolymeric outer cladding 58; ii) a portion of the polymeric outercladding 58 and a portion of the glass inner cladding 54; or iii) aportion of the polymeric outer cladding 58 and a portion of the glassinner cladding 54 and a portion of the core 18.

The core 18 may be composed of pure silica, doped silica (e.g., dopedwith germanium, aluminum, titanium, and/or chlorine) and/or otheroptically transparent materials. The glass inner cladding 54 may becomposed of pure silica, doped silica (e.g., fluorine, boron, and/ortitanium) or other optically transparent materials. The selective dopingof the core 18 and the glass inner cladding 54 used to form anevanescent optical coupler with suitably high coupling efficiency CE isdescribed in greater detail below.

The glass portion 16 has a glass-portion surface 62 that can be exposedwhen the end section 12 of the fiber 10 (shown in FIGS. 2A and 2B) isprocessed to remove some of the polymeric outer cladding 58 to form astripped end portion 28 (also shown in FIGS. 2A and 2B). In an example,this removal process is carried out prior to drawing the fiber 10. Inanother example, this removal process is carried out after fiberfabrication by locally ablating, etching and/or polishing down thefiber. Note that in some examples, the glass-portion surface 62 isformed by only the glass inner cladding 54 (FIG. 1B), while in otherexamples the glass-portion surface is formed by both the glass innercladding and the core 18 (FIG. 1A). The glass-portion surface 62 may beflat and run parallel to the central axis AC of the fiber 10 and/or mayextend coaxially with the fiber for either a portion of the fiber 10 orthe entire length of the fiber. In examples, the glass inner cladding 54along with the flat glass-portion surface 62 gives the fiber 10 a “D”shape, especially at the stripped end portion 28. In FIG. 1A, the core18 resides at the flat glass-portion surface 62. In FIG. 1B, the core 18resides a distance DS from the flat glass-portion surface. In general,the distance DS is in the range 0 μm≤DS≤4 μm, where the case of DS=0 isshown in FIG. 1A. Note that in the example of FIG. 1A, the flatglass-portion surface 62 can cut into an otherwise round core 18 so thatthe core can have a D shape and be part of the flat glass-portionsurface 62. In an example, the glass core 18 is centered on the centralaxis.

As noted above, the fiber 10 is single mode, i.e., is configured tosupport only the fundamental mode at an operating wavelength λ, which inan example can be one of the known fiber telecommunication wavelengthsas noted above. Since the fiber 10 is single mode, it has only a singlefiber effective index N_(F) and thus a single fiber propagation constantβ_(F). As discussed in greater detail below, the fiber effective indexN_(F) can fall within a range N_(F) from a target fiber effective indexvalue due to fiber manufacturing variations, including variations in theupdoping of the fiber 10. Note that a variation in the fiber effectiveindex N_(F) translates into a variation in the fiber propagationconstant β_(F) over a corresponding range Δβ_(F).

FIGS. 2A and 2B are side views and FIG. 2C is a front elevated view ofan end section 12 of the example fiber 10 of FIG. 1B and these Figuresshow the stripped end portion 28. The stripped end portion 28 has anaxial length LS (FIG. 2B). The end section 12 includes a tip 13.

FIG. 2D is a cross-sectional view of an example glass portion 16 whereinthe otherwise flat glass-portion surface 62 includes a centralprotrusion 63C that includes at least a portion of the core 18 and alsoincludes two side protrusions 63S spaced apart from the centralprotrusion. The central protrusion 63C and the two side protrusions 63Sdefine two longitudinal recesses 65S in which contaminants (particles)can move when the fiber 10 is operably engaged with waveguides of a PLC,as described below. Particle movement into the recesses 65S and awayfrom the contact points established by the central protrusion 63C andside protrusions 63S may be enhanced by providing a liquid medium (notshown) at the fiber-PLC interface during mating. For example, the liquidmedium may be an index-matching liquid that is permanent (e.g., an indexmatching gel) or temporary (e.g., isopropyl alcohol, which willevaporate rapidly after mating).

Plug Connector

FIG. 3A is a top elevated and partially exploded view and FIG. 3B is atop elevated assembled view of an example alignment assembly 104P usedto form a plug-type optical interconnection device or “plug connector”100P as shown in FIG. 5A, introduced and disclosed herein. The term“plug connector” is used to distinguish from a receptacle connectorintroduced and discussed below.

The alignment assembly 104P includes a housing 110 having a front end112, a back end 114, a top side 116, a bottom side 118, and an assemblyaxis A1 that runs in the z-direction. The top side 116 is defined by aplanar top member 130 with a front-end section 131 having a front end132, a back-end section 133 having a back end 134, a top surface 136, abottom surface 138, and opposite edges 140. The planar member 130supports two catch features (“catches”) 150 that extend outwardly fromthe edges 140 and that reside close to the front end 132, while anothercatch 150 resides on the top surface 136 adjacent the back end 134. Thehousing 110 also includes a planar bottom member 160 having a front end162, a back end 164, a top surface 166, a bottom surface 168 andopposite edges 170.

The planar bottom member 160 is attached to the planar top member 130 bytwo spaced apart guide-feature support members 200. Each guide-featuresupport member 200 includes a front end 202, a back end 204, a top side206, bottom side 208, and opposite inner and outer sides 210 a and 210b. The bottom sides 208 of the guide-feature support members areattached to the top surface 166 of the planar bottom member 160 close tothe respective edges 170, while the top sides 206 are attached to thebottom surface 138 of the planar top member 130 close to the respectiveedges 140.

Each guide-feature support member 200 includes on the inner side 210 a ahousing channel 220, which in an example runs generally from the frontend 202 to the back end 204. Each guide-feature support member 200 alsoincludes on the outer side 210 b a guide feature 224, which in anexample also runs generally from the front end 202 to the back end 204.The front ends 202 of the two spaced-apart guide-feature support members200 can extend beyond the front end 132 of the planar top member 130,with the inner sides 210 a defining a receiving area 240. The exampleguide feature 224 is raised, which makes the connector a plug connector.In another embodiment, the guide feature 224 can be recessed, so thatthe connector can also be configured as a receptacle connector. Eachhousing channel 220 has front end 222 that resides short of front end202 of the guide-feature support member 200 and that these front endsacts as a stop.

With continuing reference to FIGS. 3A and 3B, the alignment assembly104P further includes a carrier member 300 having a front end 302, aback end 304, a top side 306, a bottom side 308 and opposite edges 310.The back end 304 includes a resilient-member retaining feature 305, asexplained in greater detail below. In an example, the top side 306 canbe angled relative to the horizontal (x-z) plane. The bottom side 308can also be angled and can include a step 312 adjacent the back end 304.Thus, in an example, the carrier member 300 can be generally wedgeshaped. The carrier member 300 can also include raised guide features324 respectively disposed on the opposite edges 310 and sized tooperably engage the housing channels 220 of the guide-feature supportmembers 200. This operable engagement can be sufficiently loose so thatthere can be movement of the carrier member 300 in the y-direction whenthe carrier member is subjected to a downward (−y-direction) force, asdiscussed below.

The alignment assembly 104P also includes a resilient member 350 with afront end 352 and a backend 354, and further includes a resilient-memberretainer 400. The resilient-member retainer 400 includes a front end402, a back end 404, and opposite edges 410. The front end 402 includesa retaining feature 403 while each of the opposite edges 410 includes araised guide feature 414. In an example, the resilient member 350comprises a spring and the retaining feature 403 is a post sized toengage the back end 354 of the spring.

The alignment assembly 104P is assembled by inserting the carrier member300 into the back end 114 of the housing 110 and into the receiving area240, with the raised guide features 324 engaging the housing channels220 and moving forward until contacting the front ends of the housingchannels. The resilient member 350 is then operably positioned with itsfront end 352 engaging the resilient-member retaining feature 305 of thecarrier member 300 and the back end 354 engaging the resilient-memberretaining feature 403 of the resilient-member retainer 400. Theresilient-member retainer 400 is then urged toward the carrier member300 so that it resides on or immediately adjacent the top surface 166 ofthe planar bottom member 160, with its raised guide features 424residing within the housing channels 220 of the guide-feature supportmembers 200.

Once the resilient-member retainer 400 is inserted into the housing 110,it is held in place using an adhesive and/or a retaining clip thatallows it to snap into place. The resilient member 350 provides a forceon the carrier member 300 during connector mating, as discussed below.Note that the carrier member 300 is slidingly engaged with the housing110, with the front ends 222 of the housing channels limiting theforward movement of the carrier member. The resilient member 350 and theresilient-member retainer 400 thus make the carrier member springloaded, so that the carrier member can also be referred to has thespring-loaded carrier member for convenience.

FIGS. 4A and 4B are similar to FIG. 3B and shows the alignment assembly104P with a latch member 450 disposed toward the back end 114 of thealignment assembly. The latch member 450 has front end 452, a back end454, a top side 456, a bottom side 458, and opposite edges 460. Thelatch member has an aperture 453 that extends from the front end 452 tothe back end 454 and is sized to receive the planar top member 130. Thelatch member 450 also includes a pair of latch pins 470 that reside onthe front end 452 adjacent the opposite edges 460 and the bottom side458. The latch pins 470 that extend in substantially the same directionas the connector axis A1. The latch member 450 also includes a latchfeature 474 on the top side 456 and adjacent the back end 454.

The latch member 450 is added to the alignment assembly 104P byinserting the back end 134 of the planar top member 130 through theaperture 453, whereupon the catch 150 engages the back end 454 of thelatch member. This allows latch member 450 to slide along the planar topmember 130 in the axial direction while the catch 150 prevents the latchmember from sliding off the back end 134 of the planar member.

FIG. 5A is a top elevated view that shows alignment assembly 104P ofFIG. 4B operably disposed above an alignment ferrule assembly 500, whileFIG. 5B shows the assembled plug connector 100P formed by operablyengaging the alignment assembly and the alignment ferrule assembly. Thealignment ferrule assembly 500 includes an alignment substrate 510having a front end 512, a back end 514, a top surface 516, a bottomsurface 518, opposite edges 520, and a central axis A2. The alignmentsubstrate 510 supports an array (“fiber array”) 11 of the fibers 10 asdiscussed above. The end section 12 of each fiber 10 is supported on thebottom surface 518 of the alignment substrate 510 and runs in thedirection of the central axis A2. The fibers 10 in the fiber array 11have a fixed pitch P. In an example, a sheet of elastomeric material(not shown) can be disposed between the fibers 10 the bottom surface 518of the alignment substrate 510 to help seat the fibers and to avoid theformation of gaps when interfacing with a PLC, as described below. Inother examples discussed below, the bottom surface 518 can includeV-grooves 519 (see, e.g., FIG. 15) in which the fibers 10 reside andwhich are configured to define the fiber spacing (pitch P) and tootherwise assist in securing and aligning the fibers to a reference,such as one of the edges 520 of the alignment substrate 510.

The front end 512 of the alignment substrate 510 can be angled, i.e.,can have a V-shape defined by a front-end portion 512F of the alignmentsubstrate having converging edges while a back-end portion 514B of thealignment substrate has generally parallel edges 520. The convergingopposite edges in the front-end portion 512F can serve as exteriorreference surfaces, which are precisely aligned relative to the array 11of fibers 10.

An adhesive material 550 is provided to the top surface 516 of thealignment substrate 510. The housing 110 is then interfaced with thealignment ferrule assembly 500 by bringing the adhesive material 550 onthe alignment ferrule assembly 500 into contact with the bottom side 308of the carrier member 300. In an example, the angled step 312 of thecarrier member 300 serves as a stop that contacts the back end 514 ofthe alignment substrate 510. The bottom side 308 and the angled step 312of the carrier member 300 thus define a receiving region 316 where thealignment substrate 510 can be received by and secured to the alignmentassembly 104.

The adhesive material 550 serves to secure the alignment ferruleassembly 500 to the carrier member 300. The wedge shape of the carriermember 300 allows for the bottom side 308 of the carrier member toflatly engage the alignment substrate 510 and the adhesive material 550thereon while the housing 110 remains at an angle to the fiber array 11.In this configuration, the assembly axis A1 and the z-axis define aconnection angle φ in the y-z plane at which the plug connector 100Pengages a corresponding receptacle connector, as explained below. In theplug connector 100P, the alignment ferrule assembly 500 is used toprovide aligned fibers 10 while the alignment assembly 104P is used toprovide an aligned alignment ferrule assembly 500. This is made possibleby the above-described components of the alignment assembly 104P beingprecision-made components while the alignment substrate 510 is also aprecision-made component.

As mentioned above, the converging opposite edges in the front-endportion 512F can serve as exterior reference surfaces, which areprecisely aligned relative to the array 11 of the fibers 10. These edgesalign to mating features on the PLC receptacle so that the fibers 10 areprecisely aligned to PLC waveguides 650. The alignment assembly 104Pprovides downward force on the aligned ferrule 500 to keep its fibers 10in contact with the PLC waveguides 640 for efficient evanescentcoupling. The alignment assembly 104P also provides coarse lateralalignment of the aligned ferrule, which is sufficient to guide thealigned fiber ferrule 500 front-end portion edges 512F into matingreceptacle elements that are in turn precisely aligned to PLCwaveguides.

Example methods of forming precision-made alignment substrates 510 andalignment ferrule assemblies are discussed below.

FIG. 6A is a top elevated partially exploded view and FIG. 6B isassembled view of a PLC 600. The PLC 600 comprises a PLC substrate 610having a front end 612, a back end 614, a top surface 616, a bottomsurface 618, opposite edges 620, and a PLC axis A3. The PLC substratesupports an array 630 of optical channel waveguides (“PLC waveguides”)640, which in the example shown start at the back end 614 and runsubstantially parallel to the PLC axis A3 and terminate just beforereaching the front end 612 of the PLC substrate. In an example, the PLCwaveguides 640 reside at or near the top surface 616, and further in theexample, can constitute channel or rib PLC waveguides. The PLCwaveguides 640 have the same pitch P as the optical fibers 10 of thealignment ferrule assembly 500. As best seen in the close-up view ofFIG. 6C, each PLC waveguide 640 includes a waveguide core 641. The“cladding” of each PLC waveguide 640 is constituted by a portion 611 ofthe PLC substrate 610 that immediately surrounding the core 641. Thearray 630 of PLC waveguides 640 has first and second sides 632 definedby the two outermost PLC waveguides in the array.

The PLC 600 further includes stop fixture 660 attached to the topsurface 616 of the PLC substrate 610. The stop fixture 660 can also be araised feature on the PLC substrate, such as features created in etchedlayers of PLC substrate material, or patterned features created byphotolithographic masking and etching, or molding. The stop fixture 660has a front end 662, a back end 664, and top surface 666. The stopfixture 660 can also have a recess 663 open at the front end 662, withthe recess having an inside edge 665. In the example shown, the recess663 includes a V-shaped section 663V.

The stop fixture 660 is first coarse aligned and then fine aligned tothe PLC waveguide 640 before securing the stop fixture to the topsurface 616 using adhesive material 550, which in an example can becured using ultraviolet light (i.e., is UV-curable). The coarse and finealignment of the stop fixture 660 to the PLC waveguides 640 can becarried using various techniques. In one example, the alignment isactive and utilizes a vision system 700 and alignment marks 710S on thestop fixture 660 and alignment marks 710P on the PLC substrate 610. Inanother example, the alignment is active and is performed using opticalcoupling of light into the PLC waveguides 640 by temporarily mating thestop fixture 660 with the fiber alignment ferrule assembly 500. The stopfixture 660 and the fiber alignment ferrule assembly 500 are then movedin unison during an optical power peaking operation involvingtranslation and rotation relative to the PLC waveguides 640 whiledetecting the light outputted from the PLC waveguides.

In another example, the stop fixture 660 is passively aligned usingraised stop fixtures 712 formed on the top surface 616 of the PLCsubstrate 610 during the fabrication of the PLC waveguides 640. Theraised stop fixtures 712 can be formed using photoresist and cancomprise for example photoresist islands or etched mesas. The raisedstop fixtures 712 can also be formed using precision-formed recessessuch as etched pits, or V-grooves into which precision elements (e.g.,spheres, fibers, posts, etc.) can be disposed that can define aprecision stop at the location of the precision-formed recesses. In anexample, precision photolithographic techniques can be employed to formthe raised stop fixtures 712 so that they can provide precise alignmentof the stop fixture 660 on the PLC substrate 610.

After the stop fixture 600 is precisely aligned to the PLC waveguides640, it is secured to the PLC substrate 610 using, for example, theadhesive material 550. The adhesive material 550 forms a thin bond linebetween the stop fixture 660 and the PLC substrate 610 that limitsmotion and misalignment of the stop fixture during curing.

Receptacle Connector

FIG. 7A is top-elevated partially exploded view and FIG. 7B is anassembled view of the PLC 600 of FIG. 6B along with a receptacle adapter750 that together define a receptacle connector 100R configured tomatingly engage with the alignment assembly 104P of the plug connector100P to define an evanescent optical coupler, as explained furtherbelow.

The receptacle adapter 750 has a front end 752, a back end 754, a topside 756, a bottom side 758 and opposite edges 760. The receptacleconnector has a two spaced apart support tabs 770 that run in thez-direction. The support tabs 770 are connected by a bridge section 776that includes two vertical guide-feature support members 778 that resideon the respective inside edges of the support tabs 770. A horizontalcross member 780 connects the two vertical guide-feature support members778 so that the bridge section 776 defines an open interior (“adapterinterior”) 782 of the adapter 750.

The receptacle adapter 750 includes two spaced apart arms 800 thatrespectively extend from the vertical guide-feature support members 778and that further define the receptacle adapter interior 782. In anexample, each arm 800 resides in a y-z plane and extends at theconnection angle φ as measured in the y-z plane. In the present example,the connection angle φ>0, but the arms 800 need not be angled and in anexample can extend directly the z-direction to provide a connectionangle φ=0. In one example, each arm 800 has the form of a fork with anupper tine 802 and a lower tine 804 that define a guide feature 801 inthe form of a guide slot 803. In an example, the guide slot 803 has aflared end 805. Also in an example, the upper tine 802 has a bulbous end806 that includes a lip 808.

The receptacle adapter 750 also includes a bendable (flexible) tongue784 that extends from the center of the raised cross member 780 in thegeneral direction of the arms 800. In an example, the tongue 784 has anupwardly curved end section 786. In an example, the receptacle adapter750 can be made of metal, and further in the example can be a unitarystructure, i.e., is a single piece, as opposed to being an assembly madeof multiple separate pieces. Note also that the arms 800 of thereceptacle adapter 750 can be configured with a guide feature 801 in theform of a guide protrusion rather than a guide slot to make thereceptacle adapter a plug adapter.

The receptacle adapter 750 is attached to the top surface 616 of the PLCsubstrate 610 with the stop fixture 660 residing at least partiallywithin the adapter open interior 782. In one example, this isaccomplished by placing adhesive material 550 on either side of the PLCwaveguide array 630 and then bringing the support tabs 770 into contactwith the adhesive material. In an example, the adhesive material 550 isUV-curable and is exposed to UV light to cure the adhesive material whenproper alignment of the receptacle connector to the PLC 600 is achieved.The receptacle connector 100R can be actively and/or passively alignedwith the PLC waveguides array 630 of the PLC 600 using the same activeand passive alignment techniques described above.

In an example, UV curing of the adhesive material 550 can be facilitatedby providing holes 773 in the support tabs 770. An adhesive material 550that can be both UV and thermally cured can also be used, in which casethe receptacle adapter 750 is initially tacked into position by UVcuring the adhesive material in selected locations. After UV curing, thePLC substrate 610 and the receptacle adapter 750 are exposed to heat(e.g., placed in a thermal curing oven) to completely cure the adhesivematerial. The thin layer of adhesive material 550 joining the receptacleadapter 750 to the PLC substrate 610 is desirable to minimize shiftsduring UV and thermal curing. The resulting assembled structure of thePLC 600, stop fixture 660 and receptacle adapter 750 forms the resultingreceptacle connector 100R, as shown in FIG. 7B.

FIG. 8A shows the receptacle connector 100R of FIG. 7B along with theplug connector 100P arranged in position to operably engage thereceptacle connector 100R to form an evanescent optical coupler 900.FIG. 8B is the same as FIG. 8A but shows the assembled evanescentoptical coupler. FIG. 8C is a cross-sectional view in the y-z plane of asimplified version of the evanescent optical coupler 900 of FIG. 8Bwhere coupling angle φ=0 and that shows an evanescent coupling regionECR where the end sections 12 of the fibers 10 and the PLC waveguides640 overlap and are aligned and are in sufficiently close proximity toone another so that evanescent coupling can occur (i.e., the fibers andwaveguides are in evanescent optical communication).

With reference again to FIGS. 8A and 8B, the plug connector 100P engagesthe receptacle connector 100R at the connection angle φ so that theraised guide features 224 on the guide-feature support members 200 ofthe housing 110 enter the corresponding guide slots 803 of the arms 800.The flared end 805 of the guide slot 803 helps align the raised guidefeatures 224 into the guide slot. As the plug connector 100P andreceptacle connector 100R are urged together, the bulbous ends 806 ofthe upper tines 802 pass through the respective catches 150 at the sides150 of the planar top member 130 and cause the upper tines to deflecteddownward until the respective lips 808 pass through and engage thecatches 150. Meanwhile, the wedge-shaped top side 306 of the carriermember 300 engages the tongue 784, which is resilient and applies apressing force FD on the carrier member 300. This pressing force FD onthe carrier member 300 is downward and presses the alignment substrate510 of the alignment ferrule assembly 500 onto the PLC waveguides 630supported by the PLC substrate 610. This in turn forces the end sections12 of the optical fibers 10 to be close proximity to the PLC waveguides640 of the PLC 100. The pressing force FD increases as the plugconnector 100P is urged farther into the receptacle connector 100R andis maximum when the bulbous ends 806 and lips 808 of the upper tines 802engage the catches 150 on the housing 110 of the plug connector 100P, asshown in FIG. 8B. As noted above, the precision fabrication of thevarious components of the plug connector 100P and the receptacleconnector 100R result in precision alignment of the fibers 10 to the PLCwaveguides 640 when the plug connector and receptacle connector matinglyengage to form the evanescent optical connector 900.

Example configurations of the evanescent optical coupler 900 allow forthe pressing force FD on the alignment ferrule assembly 500 to beapplied late in the connector mating process, i.e., just as theconnection is being completed. In one example, the angled front endsection 512F of the alignment ferrule assembly 500 is operablypositioned in the V-shaped section 663V of the recess 663 of the stopfixture 660, forced into position by compression of the resilient member350. This ensures that the fibers 10 are already aligned to the PLCwaveguides 640 of the PLC 600 prior to application of the pressing forceFD. This approach ensures that after application of the pressing forceFD on the alignment ferrule assembly 500, no additional lateralalignment of the fibers 10 is needed since at this point any relativemovement risks damaging the PLC waveguides 640.

After full insertion of the plug connector 100P into the receptacleconnector 100R, the fibers 10 are aligned to the PLC waveguides 640 andare firm contact therewith due to the pressing force FD of tongue 784.This pressing force FD also reduces any gaps that might otherwise occurbetween the fibers 10 and the PLC waveguides 640.

FIG. 9 is similar to FIG. 8B and shows the latch member 450 in itslatching position, i.e., moved towards the front end 132 of the planartop member 130 so that the latch pins 470 reside in the guide slot 803of the arms 800 of the receptacle adapter 750. This prevents the uppertines 802 of the arms 800 from being deflected downward, thereby lockingthe plug connector 100P to the receptacle connector 100R. To disengagethe plug connector 100P from the receptacle connector 100R, the latchmember 450 is moved toward the back end 134 of the planar top member 130so that the latch pins 470 are removed from the guide slot 803. Thisallows the upper tines 802 of the arms 800 to be deflected downward,thereby releasing the lips 808 on the bulbous ends of the upper tines tobe released from their respective catches 150 at the edges 140 of theplanar top member 130.

Alternate Embodiments for Applying the Pressing Force

There are several other example embodiments for providing the pressingforce FD on the alignment ferrule assembly 500, as depicted in thecross-sectional views of FIGS. 10A through 10G, below. In the alternateembodiments, the pressing force FD is applied either directly orindirectly to the carrier member 300, which transfers the pressing forceto the alignment ferrule assembly 500 bonded to its bottom side 308. Thepressing force FD closes any gaps gap between the optical fibers 10 andthe PLC waveguides 540 of the PLC 100, ensuring consistent low lossoptical coupling between the optical fibers and the PLC waveguides. Notethat FIGS. 10A through 10C are similar to the simplified configurationof FIG. 8C where the connection angle φ=0, i.e., the mating engagementof the plug connector 100P and receptacle connector 100R is along thehorizontal direction.

FIG. 10A illustrates an example embodiment of the evanescent opticalcoupler 900 wherein the housing 110 of the plug connector 100P includesa connector tongue 135, which in an example can extend from the frontend 132 of the planar top member 130. The tongue 135 is configured toslip underneath the receptacle connector tongue 784 as the plugconnector 100P and receptacle connector 100R are matingly engaged. In anexample, the tongue 135 includes a wedge-shaped front end 137 tofacilitate this process. In addition, the top side 306 of the carriermember 300 includes a contact feature 330, shown by way of example asbeing dome-shaped. The contact feature 330 is configured so that thepressing force FD from overlapping receptacle connector tongue 784 andconnector tongue 135 is directed through the carrier member 300 to thealignment substrate 510 of the alignment ferrule assembly 500. The domeshape of the contact feature 330 provides strength while also allowingthe alignment ferrule assembly 500 to be free to tip and tilt while thepressing force FD is applied so that any gaps between the optical fibers10 and the PLC waveguides 640 are reduced or eliminated. The dome-shapedcontact feature 330 of the carrier member 300 be applied to any of thealternate embodiments disclosed herein. Low friction surfaces,materials, and/or lubricants can be used to minimize in-plane frictionalforces.

FIG. 10B is similar to FIG. 10A and shows another alternate embodimentof the evanescent optical coupler 900 wherein a second resilient member350′ is used to provide the pressing force FD. In this embodiment, thereis no need for the receptacle connector tongue 784. Instead, the topside 306 of the carrier member 300 includes a resilient-member retainingfeature 307 and the bottom surface 138 of the top planar member 130 alsoincludes an opposing resilient-member retaining feature 137. A secondresilient member 350 is operably supported in the y-direction by the tworesilient-member retaining features 307 and 137. The spring constant ofthe first or horizontal resilient member 350 can be selected to behigher than the spring constant of the second or vertical spring member350′. In this configuration, during the initial stage of theconnector-receptacle mating process, the alignment ferrule assembly 500is forced into contact with the stop fixture 660 by the first orhorizontal resilient member 350. Later in the connector-receptaclemating process, the second or vertical resilient member 350′ providessufficient pressing force FD to drive the fibers 10 of alignment ferruleassembly 500 into aligned contact with the PLC waveguides 540 of the PLC600 when the latch 450 is moved into the latching position (see FIG. 9).

In an example, the housing 110 can be designed to matingly engage thereceptacle adapter 750 at a connection angle φ>0 as described above, sothat the first or horizontal resilient member 350 is compressed firstwhen the alignment ferrule assembly 500 first contacts the stop fixture660, while the second or vertical resilient member 350′ is compressedlast, i.e., in late connector-receptacle connector mating process afterthe front end 512 alignment ferrule assembly 500 has contacted the stopfixture 600.

In the example of FIG. 10B, the first and second resilient members 350and 350′ are coiled springs by way of example. Other types of resilientmembers 350 and 350′ can be used, such as resilient material. FIG. 10Cis similar to FIG. 10B and shows a second resilient member 350′ in theform of a spring sheet, which can be stamped and bent to fit into thespace between the bottom surface 138 of the planer top member and thetop side 306 of the carrier member 300.

FIG. 10D is another cross-sectional view of an alternate embodiment ofthe evanescent optical coupler 900 that utilizes two horizontalresilient members 350 rather than one horizontal resilient member andone vertical resilient member. The alternate embodiment of FIG. 10D isuseful when trying to reduce the vertical size of the evanescent opticalcoupler 900. In this alternate embodiment, the resilient-member retainer400 includes two retaining features 403 that are spaced apart in thevertical direction. The lower retaining feature 403 is aligned with theretaining feature 305 at the back end 304 of the carrier member 300. Thehousing 110 also includes a second resilient-member retainer 400attached to the bottom surface 138 of the planar top member 130 and thatincludes a retaining feature 403 that opposes the top retaining feature403 of the first resilient-member retainer 400 at the back end 114 ofthe housing 110. The second resilient-member retainer 400 includes abevel 401 where the front end 402 and the bottom side 408 meet. The topside 306 of the carrier member 300 includes a wedge feature 326 thatresides towards the front end 302 of the carrier member and that isangled to match the bevel 401 of the second resilient-member retainer400.

During the connector-receptacle mating process, the lower resilientmember 350 applies a horizontal force that pushes the alignment ferruleassembly 500 into the stop fixture 660 while the upper resilient member350 pushes the second resilient-member retainer horizontally so that thebevel 401 engages the wedge feature 326. This results in the creation ofa pressing force FD on the carrier member 300, which pushes down on thealignment substrate 510 and the optical fibers 10 that resideunderneath. The length and spring constant of the second or upperresilient member 350 can be selected so that pressing force FD isapplied to the alignment ferrule assembly 500 late in theconnector-receptacle connector mating process. This approach ensuresthat the alignment ferrule assembly 500 has already been forced intocontact with the stop fixture prior to generating the pressing force FD.The latch 450 is used to secure the planar top member 130 in place tomaintain the downward force FD.

FIG. 10E is similar to FIG. 10D and illustrates another alternateembodiment of the evanescent optical coupler 900 wherein the upperresilient member 350 is removed and the upper resilient-member retainer403 is extended in the y-direction and is now referred to as extensionor beam 403. The extension 403 includes the bevel 401, which as in FIG.10B resides adjacent the wedge feature 326 of the carrier member 300.This is equivalent to the embodiment of FIG. 10D where the upperresilient member 350 has an extremely high spring constant. Theextension (beam) 403 is deflectable to provides an additional downwardspring force when the bevel 401 presses against the wedge feature 326 ofthe carrier member 300. In this embodiment, the extension 403 becomesanother example of a resilient member used to apply the pressing forceFD on the alignment ferrule assembly through the intervening carriermember 300. As in the embodiment of FIG. 10D, the latch 450 is used tosecure the planar top member 130 in place to maintain the downward forceFD.

FIGS. 10F and 10G are similar to FIG. 10D and illustrates anotheralternate embodiment of the evanescent optical coupler 900 wherein theextension 400 is replaced with a cantilevered latch extension 480 thatextends from the front end 452 of the latch member 450. The latchextension 480 has a front-end section 482 that is upwardly curved tosubstantially match the wedge angle of the wedge feature 326 of thecarrier member 300. As shown in FIG. 10F, the front-end 482 section ofthe latch extension 480 is designed to be in close proximity to thewedge feature 326 when the latch member 450 is in its unlocked position.

The latch member 450 can be moved to its locked position by sliding itover the top planer member 130 once the plug connector 100P andreceptacle connector 100R are fully engaged, as shown in FIG. 10G. Thisensures that both the latching and the generation of the pressing forceFD take place after the alignment ferrule assembly 500 is in its targetposition, i.e., with the optical fibers 10 aligned to PLC waveguides 540of the PLC 600.

As the latch member 450 is moved forward, the curved front end 482 ofthe latch extension 480 contacts the wedge feature 326, forcing thealignment ferrule assembly 500 and the optical fibers 10 downward sothat they come into contact with the PLC waveguides 540 of the PLC 600.Since the latch member 450 remains in its locked position when theevanescent optical coupler 900 is in used, the curved front end 402 ofthe latch extension 480 continues to provide the pressing force FD onthe alignment ferrule assembly 500. The latch extension 480 can befabricated from a material that will not lose its spring or creep duringlong term use. For example, the latch extension 480 can be fabricatedfrom a stiff plastic material or a metal spring material.

During the connector-receptacle connector demating process, the latchmember 450 is unlocked by moving it toward backwards, i.e., toward theback end 114 of the connector housing 110. This action removes thecurved end 482 of the latch extension 480 from the contact with thewedge feature 326 of the carrier member 330, which in turn relieves thepressing force FD applied to the alignment ferrule assembly. Thisensures that during the demating process, there are is no substantialpressing force applied to the PLC substrate 610 that could scratch ordamage the PLC waveguides 540 or the optical fibers 10.

Example Alignment Ferrule Assembly and PLC

FIG. 11A is a partially exploded bottom view of an example alignmentferrule assembly 500 showing an array of fibers 10 each having an endsection 12 where the polymeric outer cladding 58 of the cladding 22 isstripped away to reveal the glass portion 16 (see e.g., FIG. 2A). Thealignment substrate 510 is shown disposed below the glass portions 16 ofthe fibers 10, with its bottom surface 518 facing the fibers. Thealignment substrate 510 can be formed from a drawn glass sheet or rodhaving a desired cross-sectional shape and that is cut from the sheet orrod to have the desired size and shape. The alignment substrate 510 canalso be formed using one or more other processes alone or incombination, such as a fusion draw process, a redraw process, ahot-pressing process and a flame working process. Examples of formingthe alignment substrate 510 as a precision component that allows forprecision alignment are described in greater detail below.

FIGS. 11B and 11C are bottom and top views of the resulting alignmentferrule assembly 500, with the glass portions 16 bonded to the bottomsurface 518 of the alignment substrate using an adhesive material 550.In an example, the adhesive material is curable using ultraviolet (UV)light (i.e., is UV-curable). This is facilitated by the use of aUV-transparent alignment substrate 510.

FIG. 11D is a cross-sectional view of an example alignment ferruleassembly 500 wherein the alignment substrate 510 acts as a shapingmember that shapes each fiber 10. This shaping is also accomplished byselectively removing portions of the glass inner cladding so that theend section 12 of each fiber 10 is flat against the bottom surface 518of the alignment substrate 510 while the portion of the fiber thatextends out from the back end 514 of the alignment substrate is angledrelative the horizontal. In an example, the tip 13 of the end section 12can be bent upward by leaving a small portion of the polymeric claddingin place at the tip as shown.

FIG. 12A is a top-down view of an example PLC 600 and FIG. 12B is an x-ycross-sectional view of the example PLC 600 of FIG. 12A as taken at theline B-B in FIG. 12A. The PLC substrate 610 of the PLC 600 includes aglass-based slab 650 with a top surface 652, and an overclad layer 654on the top surface 652 and that defines the PLC substrate top surface616. The cores 641 of the PLC waveguides 640 are supported in or on theglass-based slab 650. The overclad layer 654 includes alignment channels656 that are aligned with the PLC waveguides 640, which in example havetapered end sections 642 having a tip 643 and that reside and terminatewithin the alignment channels. The alignment channels 656 have ends 657and opposite side walls 658. A stop fixture 660 is disposed adjacent thechannel ends 657. In an example, the stop fixture 660 has an L-shape,with one length of the L oriented in the y-direction and runningadjacent and parallel to an outermost alignment channel 656.

FIG. 13A is a cross-sectional view of the alignment ferrule assembly 500of FIG. 21C along with the example PLC 600 of FIG. 12B while FIG. 13B isa top-down view of the alignment ferrule assembly and the PLC 600 ofFIG. 13A, illustrating how the alignment ferrule assembly 500 is used toalign the fibers with the PLC waveguides 640 of the PLC 600. The endsections 12 of the fibers 10 supported by the alignment substrate 510are inserted into their respective alignment channels 656 in theoverclad layer 654 of the PLC substrate 610. Note that in the examplealignment ferrule assembly 500, spacer fibers 10S are used to ensurethat the fibers 10 have the same pitch P as the PLC waveguides 640. Theend sections 12 of the fibers 10 move toward the back ends 657 of thealignment channels 656 so that the end sections overlap with the taperedends 642 of the PLC waveguides 640. The front end 512 of the alignmentsubstrate 510 contacts the stop fixture 660 disposed at or adjacent thechannel ends 657 when the fiber end sections 12 are aligned with andoverlap respective PLC waveguides 640.

FIGS. 14A and 14B are cross-sectional views of an example ferruleassembly 500 wherein the glass portion 16 of each fiber 10 has a keyholecross-sectional shape with a dovetail section 82 that includes analignment surface 70 and a bulbous section 84 that includes the flatglass-portion surface 62. The alignment ferrule assembly 500 includesmultiple spaced-apart (e.g., interdigitated or interleaved) spacers 88supported on the top surface 516 of the alignment substrate 510 and thatdefine the period P of the fibers 10. In an example, the spacers 88 areoptical fibers, i.e., spacer fibers 10S. The dovetail sections 82 of theglass portions 16 of the fibers 10 reside between the spacers 88, withthe flat alignment surfaces 70 in contact with the top surface 512 ofthe alignment substrate 510, while the flat glass-portion surfaces 62 ofeach fiber 10 face upward.

An adhesive material 550 can be used to secure the spacers 88, thealignment substrate 510 and the dovetail sections 82 of the glassportions 16 to one another. Squeezing forces FS can be applied in thehorizontal and vertical directions while the adhesive material 550 cures(e.g., via UV radiation). A temporary pressing member 90, such as aglass sheet, can be employed at the flat glass-portion surfaces 62 tofacilitate the even application of the vertical squeezing forces FS andto set the dovetail sections 82 within the spacers 88 and the adhesivematerial 350.

After the adhesive material 550 is cured (e.g., via exposure to UVradiation), the temporary pressing member 90 can be removed, exposingthe flat glass-portion surfaces 62 of the keyhole-shaped glass portions16 of the fibers 10 in the alignment ferrule assembly 500, as shown inFIG. 14B. The alignment ferrule assembly 500 can then be flipped over sothat the flat glass-portion surfaces 62 face downward. Since the squeezeassembly approach ensures that the glass portions 16 of the fibers 10are arranged on the precise period P and the flat glass-portion surfaces62 can be aligned to the same-period alignment channels 656 of the PLC600 in the manner discussed above. Likewise, the outside (outermost)spacers 88 provide reference datum surfaces that have a precise offsetDS relative to the cores 18 of the fibers 10. In an example, the outsidespacers 88 make contact with the stop fixture 660 (e.g., the L-sectionthat runs parallel to the alignment channels 656) to provide precisealignment of the fibers 10 with the PLC waveguides 560 of the PLC 600.Another datum surface can be formed on the alignment substrate 510 whenthe optical fibers 10 are cleaved and polished.

Laser-Produced Bumps for Alignment Ferrule Assembly

FIG. 15 is a cross-sectional view of an example alignment ferruleassembly 500 shown with one of the end sections 12 of the fibers 10residing within the alignment channel 656 of the PLC substrate 610, andwith a portion of the stop fixture 660 shown residing adjacent thealignment channel. The edge 520 of the alignment substrate 510 residesimmediately adjacent the stop fixture 660 and includes an alignment bump526 sized to provide a select amount of offset h of the alignmentsubstrate relative to the stop fixture 660 so that the fiber cores 18are aligned with cores 641 of the PLC waveguides 640. This enableslow-cost fabrication of the alignment ferrule assembly 500, since itsside surfaces can be fabricated with a relatively imprecise process,such as by dicing.

Alignment bumps 526 with precise heights h (e.g., to within ±0.5 μm) canbe formed on the surfaces (e.g., edges 520) of glass alignmentsubstrates 510 using laser bump technology as is known in the art.In-situ measurements of bump heights h to ±0.1 μm can be made using, forexample a commercially available scanning laser profilometer. Byalternating bump formation and bump height measurements, one or morealignment bumps 526 can be formed with high precision and to arbitraryheights h over a height range 0<h≤100 μm using a small number of processiterations (e.g., 3 to 4). The alignment bump formation process can becarried out rapidly (with a few seconds), while alignment bump heightmeasurements can take between 5 to 10 seconds.

Thus, in an example, at least one alignment bump 526 can be formed onthe edge 520 of the alignment substrate 510 to provide a precisionoffset datum (reference) feature. Alignment bumps 526 are attractivebecause they enable displacement of debris that may collect betweenmating datum surfaces away from contact points. The small size of thealignment bump 526 also enables high contact pressures that can compressdebris that is not displaced. Using an alignment substrate 510 withV-grooves on the bottom surface 518 has an advantage in that thealignment bump 526 can be formed prior to insertion of the fiber ends 12into the V-grooves.

FIG. 16 is a schematic diagram illustrating an example apparatus 96 andassociated method for forming alignment bumps 526 using laser light.During laser formation of an alignment bump 526, the optional V-groove519 in the bottom surface 518 of the alignment substrate 510 can be usedto precisely align the alignment substrate in a support fixture 920. Thesupport fixture 920 includes a V-groove 921 that supports either thefiber 10 or an alignment fiber 10A. The apparatus 96 includes a laserprofilometer 950 is mounted on a rigid base 954 so that it can measurethe height of laser-produced alignment bumps 256 formed on the edge 520of the alignment substrate 510. A movable mirror 956 can be moved upwardto reflect laser light 960 from a laser delivery fiber 962 and a lens964 into a target location at the edge 520 of the alignment substrate510. After forming the alignment bump 256, the movable mirror 956 can bemoved downward to allow the laser profilometer 950 to measure the heightof the bump. This process can be repeated until the alignment bump 526has the desired height corresponding to a desired precision horizontaloffset.

An advantage of using one or more precision-formed alignment bumps 526is that it allows an accurate geometrical relationship to be establishedbetween the location of fibers 10 in the V-groove 519 of the alignmentsubstrate 510 and the alignment bump 256 on the side of the alignmentsubstrate. The geometrical relationship (e.g., the distance GR in FIG.16) can be determined by forming the alignment bump 256 and thenmeasuring light coupled into the glass fiber core 18 of a given fiber 10via, for example, another optical fiber (not shown) that is preciselyscanned over the glass core in a fixture that also provides a preciseedge stop datum feature. This process enables the formation of precisionedge alignment features to an alignment substrate 510 that might nothave been formed using precision-based techniques.

Alignment bumps 526 can also be formed on other locations of thealignment substrate 510 using a similar approach. FIG. 17 is similar toFIG. 13B and shows three alignment bumps 526 on the alignment substrate510 that align with two different surfaces of a U-shaped stop fixture660. The example stop fixture 660 has an angled opening at the front end662 that enables initial coarse alignment of the alignment ferruleassembly 500 to the PLC 600. The three alignment bumps 526 can bedistributed as shown, where two alignment bumps are provided on theright edge 520 of the alignment substrate 510 while one bump is providedat the front end 512. Other numbers and locations of alignment bumps 526can also be effectively employed. An arrow DA shows the insertiondirection of the alignment ferrule assembly 500 into the angled openingat the front end 662 of the stop fixture 660 and the fibers 10 into theflared alignment channels 656.

Alignment Substrate Formed by Drawn Glass Process

In an example, the alignment substrates 510 can be fabricated using aglass drawing process, which allows for the resulting alignmentsubstrates to have at least one precision surface that can be used toestablish precision alignment of the fibers 10 to the alignmentsubstrate.

FIG. 18A is a schematic diagram of an example drawing system 580 forproducing the alignment substrates 510 as employed herein. The drawingsystem 580 may comprise a draw furnace 582 for heating a glass preform510P. The glass preform 510P has generally the same relative shape asthe alignment substrate 510 but is much larger, e.g., 25X to 100Xlarger. Thus, in an example glass preform 510P can have any suitablecross-sectional shape, and the square cross-sectional shape of the glasspreform of FIG. 18A is shown by way of example and ease of illustration.The glass preform 510P can be made using a large, uniform piece ofglass. An example of such a glass is a borosilicate glass. Another typeof glass is fused quartz. Other types of glasses can also be effectivelyemployed.

The large piece of glass can be machined to have the desired shape,e.g., a generally rectangular cross-sectional shape with precisionfeatures, as explained below. In an example, at least a portion of theglass preform 510P can be polished, e.g., laser polished. Theconfiguration of the glass preform 510P and the various drawingparameters (draw speed, temperature, tension, cooling rate, etc.)dictate the final form of the alignment substrate 510.

In the fabrication process, the drawn glass preform 510P exits the drawfurnace 582 and has the general form of the alignment substrate 510 butis one long continuous long glass member or glass sheet, referred togenerally as long glass member 510G. After the long glass member 510Gexits the draw furnace 582, its dimensions can be measured usingnon-contact sensors 584A and 584B. Tension may be applied to the longglass member 510G by any suitable tension-applying mechanism known inthe art.

After the dimensions of the long glass member 510G are measured, it maybe passed through a cooling mechanism 586 that provides slow cooling ofthe long glass member. In one embodiment, the cooling mechanism 586 isfilled with a gas that facilitates cooling of the long glass member 510Gat a rate slower than cooling the long glass member in air at ambienttemperatures.

Once the long glass member 510G exits the cooling mechanism 586, it canbe cut into select lengths called “canes” that are relatively long (tensof millimeters to 1.5 m) and then cut again into the smaller lengths todefine the individual alignment substrate 510.

In an example, the long glass member 510G can be fabricated byperforming a first draw process using the glass preform 510P to form anintermediate-sized glass preform, and then re-drawing theintermediate-sized glass preform using a second draw process to form thelong glass member 510G. The alignment substrates 510 formed using aglass drawing process have precision surfaces that can be used forestablishing alignment between the fibers 10 and the PLC waveguides, asexplained in greater detail below.

FIG. 18B is a top elevated view of an example alignment substrate 510that has been cut from the long glass member 510G (or a cane, which is aportion of the long glass member) formed using the drawing system ofFIG. 18A. The long glass member 510G is in the form of a glass sheet andso is referred to hereinafter as the glass sheet 510G. The glass sheet510G has a front end 512G, a back end 514G, a top surface 516G, a bottomsurface 518G, edges 520G and a longitudinal axis A2G. The glass sheet510G can be drawn with precision features 521G, such as along one orboth of its edges 520G. The precision features 521G of the glass sheet520G become precision features 521 of the alignment substrate 510 formedfrom the glass sheet and can serve as datum surfaces when mating thealignment ferrule assembly 500 to the PLC 600.

In the example of FIG. 18B, one edge 520G of the glass sheet 510G has aprecision feature 521G in the form of a small ridge. The curved shape ofthe ridge is designed to contact a portion of the stop fixture 660 alonga single contact line. Using a small-radius ridge ensures that debriscan flow away from the contact line, or that it can be compressed by amating force concentrated along the contact line. In an alternative edgeprofile design, the radius of the ridge can be increased so that theprecision feature 521G extends across the entire edge 520G of the glasssheet 510G and thus the entire edge 520 of the alignment substrateformed from the glass sheet. The precision feature 521G can also beformed on both edges 520G as noted above so that the alignment substratehas two corresponding precision features 521G.

In an example, the glass sheet 510G can be cut perpendicular to itslongitudinal axis A2G to form the alignment substrates 510, as well asother parts. Each alignment substrate 510 has at least one precisionflat surface (e.g., top surface 516 or bottom surface 518 and/or one orboth of the edges 520) that can be used for mounting the fibers 10during assembly of the alignment ferrule assembly 500. Alternatively, ifthe top and bottom surfaces 516G and 518G of the glass sheet 510G arenot sufficiently flat, then they can be polished in an additional apolishing step. In an example, this polishing step is performed in amanner that does not alter the precision features 21 of the alignmentsubstrates 510 cut from the given glass sheet 510G.

Other features can be added to the top or bottom of the glass sheets510G, such as V-grooves 519G fabricated on a precise pitch. TheseV-grooves 519G can be formed via a precision drawing process (e.g., byadding similar V-grooves to the glass preform), or by diamond sawing theglass alignment substrate after drawing (e.g., before or afterperpendicular cutting into individual alignment substrate parts). TheV-grooves 519G of the glass sheet 510G become the V-grooves 519 of thealignment substrate 510.

FIG. 19 is similar to FIG. 15 and shows an example alignment ferruleassembly 500 wherein the alignment substrate 510 has been formed from adrawn glass sheet 510G similar to that shown in FIG. 18B. The alignmentsubstrate 510 includes on one edge 520 a precision feature 521 in theform of a ridge. The alignment substrate 510 also includes a V-groove519 formed in the bottom surface 518 and sized to accommodate an angledalignment surface 70 of the glass portion 16 of the end section 12 ofthe fiber 10. In an example, the alignment ferrule assembly 500 includesmultiple fibers 10 each disposed in a V-groove 519, and with each fiber10 residing in a separate alignment channel 656 of the PLC 600. Theexample alignment channel 656 of FIGS. 15 and 19 is wider than the endsection 12 of the fiber 10 so that there some room for positioning theend section of the fiber when aligning and interfacing the alignmentferrule assembly 500 to the PLC 600.

An advantage of forming a precision feature 521G in the glass sheet 510Gis that it gives each alignment substrate 510 can have a primaryreference datum surface or feature that is expected to be extremelylinear due to the nature of the glass draw process. This primary datumsurface or feature can be used in forming additional datum surfaces. Forexample, the process to cut drawn glass sheets 510G into individualalignment substrate parts can leverage the precision feature 521G as areference surface or feature so that the cut is exactly perpendicular tothe edge 520G.

The process for drawing glass sheets 510G and then cutting them to formthe alignment substrates 510 can be used to create other cross-sectionalshapes that enable passive alignment of the alignment ferrule assembly500 to the PLC 600. FIG. 20 is similar to FIG. 18B and shows an exampleglass sheet 510G having angled or tapered edges 520. The angle creates aglass sheet 510G that is wider at the bottom surface 518G than at thetop surface 516G. The angled edges 520G can be used to help retain thefibers 10 in contact with the PLC waveguides 640 of the PLC 600.

FIG. 21A is a top elevated and partially exploded view of an examplealignment ferrule assembly 500 formed using the alignment substrate 510of FIG. 20. FIG. 21B shows the example alignment ferrule assembly 500 ofFIG. 21A operably arranged above an example PLC 600. FIG. 21C is thesame as FIG. 21B, except it shows the assembled structure. The alignmentferrule assembly 500 is aligned to the PLC waveguides 640 of a PLCsubstrate 610 of the PLC 600 using one or more resilient gripperelements (“grippers”) 980 disposed on the top surface 616 of the PLCsubstrate 610 and around the ends 642 of the PLC waveguides 640 todefine an example stop fixture 660. In an example, the grippers 980 areformed from a low-modulus photoresist material using photolithographictechniques. In an example, the grippers 980 are formed from a polymer. Alithographic shadow mask opaque in the regions where the grippers 980are to be formed can be aligned to previously formed PLC waveguides 640of the PLC 600 so that it is centered over the evanescent couplingregion ECR.

To precisely align the mask to the PLC waveguides 640, it may benecessary to pre-etch a window in the photoresist material over the PLCalignment marks 710P. The vision system 700 used to observe PLCalignment marks 710P can be mounted on a precision vertical stage with alinear runout<0.5 μm, so that the PLC and mask alignment marks, whichwill be located in different horizontal planes relative to the PLCplane, can be accurately aligned to each other. Alternatively, the PLCand mask alignment marks may be aligned using a split-field or dualobjective optical system that simultaneously views the alignment markslocated at different locations offset by a precise lateral offset.

After contact mask alignment, the positive photoresist is exposed to UVradiation by an UV source that is directed onto the PLC substrate 610from an off-normal axis (e.g., 10-20° off normal). Simultaneously, thePLC substrate 610 is rotated on a stage so that the unexposed regionwithin the photoresist forms a vertical taper structure that is wider atthe top (where it contacts the shadow mask) than the bottom (where itcontacts the top surface 616 of the PLC substrate 610). Photoresistregions that have been sufficiently exposed to UV will become soluble indeveloper, allowing the photoresist to only remain in the unexposedtaper regions directly beneath the shadow mask.

The grippers 980 define the recess 663, which is sized to receive thealignment substrate 610. In an example, the recess 963 is slightlysmaller than the alignment substrate 510, i.e., the grippers 980 providean interference fit for the alignment substrate. This allows the edges520 of the alignment substrate 510 to laterally deflect the grippers 980as it is pushed down into the recess 663. In an example, the grippers980 that run parallel to the PLC waveguides 640 have angled inside edges965 that are complementary to the angled edges 520 of the alignmentsubstrate 510 so that the two complementary angled edges engage toprovide self-centering of the alignment substrate in the recess 663.This self-centering is designed to cause in the fibers 10 to laterallyalign with the PLC waveguides 640 of the PLC 600. The remaining grippers980 cause the fiber 10 to axially align with the PLC waveguides 640 ofthe PLC 600. The angled inside edges 665 of the grippers 980 alsoprovide a pressing force FD on the alignment substrate 520, which helpskeep the fibers 10 in evanescent communication with the PLC waveguides640.

Alignment Substrates Formed by Drawing a Long Glass Member

FIGS. 5A and 5B discussed above show an example alignment substrate 510having an angled (V-shaped) front-end section 512F. FIG. 22 is abottom-up view of the example alignment substrate 510 and fibers 10 usedto form the example alignment ferrule assembly 500, with the tips 13 ofthe fibers 10 residing at the transition between the front-end section512F and the back-end section 514B.

FIG. 23 shows an example long glass member 510G used to form V-shapedalignment substrates 510. The example long glass member 510G has across-section with five sides, including two angled edges 510 in afront-end section 512FG that define the V-shaped front-end section 512.The long glass member 510G is formed by drawing a preform 510P havingthe same cross-sectional shape but having larger overall dimensions, asdescribed above. The alignment substrate 510 is formed by cutting thelong glass member 510G perpendicular to its long axis. The two anglededges 520F of the resulting alignment substrate 510 are datum surfacesthat can be used to establish alignment of the fibers 10 of thealignment ferrule assembly 500 with the PLC waveguides 640 of the PLC600.

FIG. 24A is a top-down view of an example PLC 600 similar to that shownin FIG. 12A and that includes an example stop fixture 660 with aV-shaped recess 663 sized to closely accommodate (receive) the V-shapedfront-end section 512 of the alignment substrate 510 of the alignmentferrule assembly 500 of FIG. 22. The stop fixture 660 may be fabricatedon the top surface 616 of the PLC substrate 610 and aligned to theevanescent coupling region ECR. The stop fixture 660 can be a raisedmesa region formed by selective etching of a deposited layer material,such as a photoresist layer, an oxide layer, or an epitaxially depositedlayer. The stop fixture 660 may extend 5 μm to 20 μm above the topsurface 516 of the PLC substrate 510. In an alternative configuration,the stop fixture 660 is a thicker raised mesa (e.g., 50 μm to 150 μmthick) formed via photolithographic exposure and etching/developmentprocesses, including the previously mentioned polymer gripperfabrication process. In an example, the recess 663 of the stop fixture660 can have a flared open end at the front end 612 of the PLC substrate610 to facilitate the insertion of the alignment ferrule assembly 500into the recess for coarse alignment of the fibers 10 to the PLCwaveguides 640.

When the angled front-end section 512F of the alignment substrate 510resides tightly within the V-shaped recess 663 as shown in FIG. 24B, thefibers 10 are in lateral and axial alignment with the PLC waveguides 640of the PLC 600.

FIG. 24C is similar to FIG. 23A and shows the addition of alignmentbumps 526 at different positions on the edge 520 of the V-shapedfront-end section 512F of the alignment substrate 520. Three suchalignment bumps 526 are shown that provide three precision contactpoints with the stop fixture 660. As described above, the alignmentbumps 526 can facilitate the precise alignment of the V-shaped alignmentferrule assembly 500 to the stop fixture 660 and make the alignment lesssensitive to debris that might become trapped between alignmentsurfaces.

As discussed above, in one example the V-shaped alignment substrate 510can be formed by cutting the V-shaped long glass member 510Gperpendicular to its long axis. In another example illustrated in FIG.25A and FIG. 25B, the V-shaped long glass member 510G can be cut in adirection that is not perpendicular to its long axis A2G. The resultingalignment substrates 510 can have its front end 512 as well as its edges520 angled in a manner such that top surface 516 of the alignmentsubstrate is smaller than the bottom surface 518, as can be seen in thecross-sectional view of FIG. 25C, which is taken along the center lineCL. This not only gives the front-end section 512F of the alignmentsubstrate a V-shape, but also adds a wedge shape in the y-z plane thatcan be exploited in the manner discussed below.

FIG. 26A is a top-down view of an example PLC 600 that includes anexample stop fixture 660 with a V-shaped recess 663 but where a topsurface 666 of the stop fixture is larger than a bottom surface 668 ofthe stop fixture so that there is an overhang at the inside edge 665 ofthe recess. In an example, the stop fixture 660 can be formed usingpolymer material and further in an example can be formed as an assemblyof the aforementioned grippers 980 such as shown in FIGS. 21B and 21C.The result is that the inside edge 665 of the recess 663 of stop fixture660 has a wedge shape that complements (accommodates) the wedge shapedfront end 512 of the alignment substrate 510 so that the respectiveedges of the alignment substrate and the stop fixture either makeface-to-face contact or line contact. This is also shown in the top-downview of FIG. 26B, which includes the alignment ferrule assembly 500 ofFIG. 25B, and in the y-z cross-sectional view of FIG. 26C, which istaken along the centerline CL. Note that the inside edge 665 has anangle relative to the planar top side 666 of the stop fixture 660 thatis other than 90° and in the example of FIG. 26C makes an obtuse anglewith the planar top side.

An advantage of using polymer grippers 980 to form the stop fixture 660is that the grippers can be precisely aligned to previously fabricatedPLC layers using alignment marks or fiducials. Typical mask alignmentequipment can achieve layer misalignments of <0.5 μm. Polymer grippersare fabricated from photosensitive material so that, using correctexposure and development conditions, an overhang region can be createdusing an undercut etch process.

Since the stop fixture 660 can be fabricated from an elastic materialsuch as a polymer, the inside edge 665 of the recess 663 can deflectlaterally as the alignment substrate 510 is inserted into the recess.The deflection causes the stop fixture 660 to create a lateral restoringforce that tends to self-center the inserted alignment substrate 510along the centerline CL. This self-centering process occurs even if thestop fixture 660 has been slightly underetched or overetched, since theunderetch or overetch is nominally identical for both opposite sides ofthe inside edge 665 of the recess 663.

FIG. 26D is a cross-sectional view similar to FIG. 26C and shows anexample where the wedge angle associated with the overhang of the insideedge 665 of the recess 663 of the stop fixture 660 is greater than thewedge angle of the edges 520 at the front-end end section 512F of thealignment substrate 510. This creates a line of contact between the stopfixture 660 and the alignment substrate 510 within the V-shaped recess663 of the stop fixture. Elastic deflection of the stop fixture 660during mating helps ensure that the alignment ferrule assembly 500 andthe fibers 10 supported thereby are rotationally as well as laterallyaligned to the PLC waveguides 640 of the PLC 600 in the evanescentcoupling region ECR.

When the evanescent coupling region ECR is located away from theV-shaped front-end section 512F of the alignment substrate 510, then anadditional pressing force FD can be applied to the alignment ferruleassembly 500, either directly over the evanescent coupling region ormore toward the back end 514 of the alignment substrate 510. On theother hand, the alignment substrate 510 can be sized such that theevanescent coupling region ECR resides completely within the V-shapedfront-end section 512F (i.e., the triangular region created by theV-shaped tip) of the alignment substrate 510. In this case, theinteraction of the V-shaped front end 512 with the flexible stop fixture660 can apply sufficient pressing force FD at the evanescent couplingregion ECR to close any gaps that might otherwise exist.

If the evanescent coupling region ECR resides outside the V-shapedfront-end section 512F of the alignment substrate 510, then anotherapproach for applying the pressing force FD is to add two additionalangled faces at or toward the back end 514 of the alignment substrate,i.e., away from the V-shaped front-end section, as illustrated in FIGS.27A and 27B. FIG. 27A is a front elevated view of an example long glassmember 510G having the necessary cross-sectional shape for forming thedesired alignment substrate 510 and includes two triangular protrusions523G. The example alignment substrate 510 of FIG. 27B includes twotriangular protrusions 523 at the back-end section 514B, which gives thealignment substrate four angled edges 520, with two at the front-endsection 512F and two at the back-end section 514B.

FIG. 28 is similar to FIG. 26B and shows an example alignment ferruleassembly 500 that employs the alignment substrate 510 of FIG. 25B andalso shows an example PLC 600 that includes a stop fixture 600 whereinthe recess 663 has a complementary shape to the alignment substrate.When the four angled edges 520 of the alignment fixture 510 engage thefour corresponding portions of the inside edge 665 of the recess 663 ofthe stop fixture 660, the entire alignment substrate is forced downward,regardless of where the evanescent coupling region ECR falls relative tothe alignment substrate. This design for the alignment substrate 510simplifies the design of the connector housing 110, since during matingof the alignment ferrule assembly 500 to the PLC 600 the connectorhousing only has to provide a low-angle force that is roughly parallelto the top surface 516 of the PLC substrate 510.

FIGS. 29A through 29E show alternate embodiments (configurations) forthe alignment substrate 510 of the alignment ferrule assembly 500 andfor the stop fixture 660 of the PLC 600. FIG. 29A is a top-down viewthat shows an example alignment substrate 510 wherein the front end 512includes beveled corners 513 and wherein the stop fixture 660 is formedby two posts 667 each having an angled facet 668 configured to makeface-to-face contact with beveled corners 513.

FIG. 29B is a top-down view that shows an example alignment substrate510 wherein the front end 512 has a V-groove 527, and wherein the stopfixture 660 is defined by a single element having angled facets 668 thatform a V-shape recess 663 that is complementary the V-groove front-endsection 512F of the alignment substrate 510.

FIG. 29C is a top-down view that shows an example alignment substrate510 wherein the front end 512 has two spaced apart recesses in the formof V-grooves 527 while the stop fixture 660 is defined by spaced apartposts 667 sized to be closely received by the V-grooves 527 of thealignment substrate 510.

FIG. 29D is a top-down view that shows an example alignment substrate510 wherein the front end 512 is squared off and wherein the stopfixture 660 has a U-shaped recess 663 sized to receive the squared offfront end of the alignment substrate.

FIG. 29E is a top-down view that shows an example alignment substrate510 wherein the front end 512 is squared off, wherein the opposite edges520 each includes a notch 529, and wherein the stop fixture 660 isdefined by spaced apart posts 667 configured to engage the notches whenthe alignment substrate is pushed through the space between thealignment posts. In an example, the posts 667 are flexible so that theydeflect when the alignment substrate passes between the posts, with theposts deflecting back into the notches 529 when the notches align withthe posts.

Other embodiments for the alignment substrate 510 can includecombinations of V-shaped front ends 512 and notches 529. For example, arectangular side notch 529 similar to the one shown in FIG. 29D can beadded to a V-shaped alignment substrate so that, once the alignmentsubstrate is pushed a sufficient distance into the V-shaped section 663Vof the recess 663 of the stop fixture 660, an additional polymer grippercan snap into the side rectangular notch to temporarily or permanentlylock the alignment ferrule assembly in position on the PLC 600.

A glass drawing process such as described above can also be used to formholes in drawn long glass members 510G, where the long glass members areused to form alignment substrates 510 that have holes with precisediameters and positions relative to other features. FIGS. 30A and 30Bare top-downs view of two example alignment ferrule assemblies 500 thateach includes two spaced apart holes 570 that run through from the topsurface 516 to the bottom surface 518 of the alignment substrate 510(i.e., the holes 570 are through holes). In another fabrication processbased on patterning/etching of glass sheets, the holes 570 may be blindholes that extend from one surface to a location within the stopfixture. The stop fixture 660 of the PLC 600 can be defined by twospaced-apart posts 667 that have the same spacing and substantially thesame diameter as the holes 570 in the alignment substrate 510 so thatthe posts can fit at least partially through the holes.

If the posts 667 are relatively rigid, they can be fabricated with adiameter that is slightly less than the diameter of the holes 570, asshown in FIG. 30A. Alternatively if the posts are fabricated from adeformable material, they can be sized to have a top surface diameterthat is slightly larger than the diameter of the holes 570 and a bottomdiameter (where they contact the PLC substrate top surface 516) that issmaller than the holes. During attachment of the alignment ferruleassembly 500 to the PLC 600, the deformable posts 667 deform slightly asthey are pushed through their respective holes 570. Since the deformableposts 667 have a relatively low elastic modulus, they can tolerate somelateral displacement when mating the alignment ferrule assembly 500 tothe PLC 600. One mated, the posts 667 within the holes 570 will work toprecisely align the fibers 10 to the PLC waveguides 640 of the PLC 600in the evanescent coupling region ECR as their deformation stressesrelax.

FIG. 30B shows an example configuration where one hole 570 is circularand the other hole is oblong. The oblong hole 570 provides room formovement of the post within the hole so that the fibers 10 can bealigned with the PLC waveguides 640 by adjusting the position of thealignment ferrule assembly 500. Using an oblong hole 570 also preventsany over-constraint of the posts 667 relative to the holes 570 thatmight otherwise occur if the post pitch is slightly different than thatof the hole pitch due to fabrication variations.

Both holes 570 can be made oblong, as shown in FIG. 30C. The oblongholes 570 can be sized to match the dimensions of oblong posts 667. Ifthe width of the oblong holes 557 is varied along their lengths, then atapered or keyhole-shaped hole can be created as shown in FIG. 30D. Inthis case, the polymer gripper post can be sized to fit through thewider portion of the oblong hole 570 but be trapped in the narrow partof the oblong hole when the alignment substrate is moved accordingly.This movement simultaneously aligns the fibers 10 to the PLC waveguides640 and also generates a pressing force FD on the alignment substrate.

A variant of the alignment substrate 510 of FIG. 30C shown in FIG. 30Dhas oblong holes that have different sized regions, with the largerregion allowing for coarse alignment with the posts 667 and the smallerregion allowing for finer alignment.

Stop Fixture Fabrication Using a Glass Drawing Process

In an example, a glass drawing process can be used to create precisionshapes can be used to form the stop fixture 660 discussed above. FIG.31A is a top elevated view of an example rod-like long glass member 660Gformed using a glass drawing process from a similarly shaped but largersized glass preform as discussed above in connection with FIG. 18A. Anexample unitary (i.e., single piece) stop fixture 660 is also shown andis formed by cutting the long glass member 660G. The example stopfixture 660 includes a V-shaped recess 663 such as discussed above (see,e.g., FIGS. 6A, 6B).

FIG. 31B is similar to FIG. 31A and shows how a multi-piece stop fixture660 can be formed from a long glass member 660G, wherein the long glassmember is cut into individual parts that can then be combined to formthe stop fixture. In the present example, the long glass member 660Gsupplies two parts 666 that are combined to form a two-part stop fixture660 having the V-shaped recess 663.

FIG. 32 is a top-elevated view that shows how the stop fixture 660aligns the alignment ferrule assembly 500 to PLC waveguides 640 of thePLC 600 by closely receiving the V-shaped front end 512 of the alignmentsubstrate 510 in the V-shaped recess 663 of the alignment fixture 660.As noted above, the alignment substrate 510 and the stop fixture 660 canhave one or more complementary sloped or tapered sides that closelyengage when the alignment substrate 510 is operably situated within therecess 663 of the stop fixture 660, which can provide a pressing forceFD that presses the fibers 10 onto the PLC waveguides 640 of the PLC600.

Alignment Ferrule Assembly with Alignment Assembly

FIG. 33A is a top elevated view of an example alignment ferrule assembly500 shown disposed beneath an alignment assembly 104. The alignmentsubstrate 510 of the alignment ferrule assembly 500 includeslongitudinal V-grooves 519 on the bottom surface 518 to providelongitudinal alignment and a select spacing (pitch) of the fibers 10.

The alignment assembly 104P includes a planar top member 1110 having acentral axis A3, a front end 1112, a back end 1114, a top surface 1116,a bottom surface 1118 and opposite edges 1120. The alignment assembly104P also includes spaced apart guide-feature support members 200 in theform of guide tubes attached to the bottom surface 1118 adjacent therespective sides 1120. Each guide tube 200 has a front end 1132, a backend 1134 and a longitudinal bore 1136 having a bore axis AB that runssubstantially parallel to the central axis A3. In an example, the frontand back ends 1132 and 1134 of the guide tubes 200 substantiallycoincide with the front and back ends 1112 and 1114 of the planar topmember 1110. In an example, each bore 1136 supports a guide pin 1140having a front-end section 1142 that extends beyond the front end 1112of the planar top member 1110. In an example, one or more of the planartop member 1110, the guide tubes 200 and the guide pins 1140 are made ofglass. In one example, the planar top member 1110 and the guide tubes200 are made of glass while the guide pins 1140 are made of materialother than glass, such as a rigid polymer or metal. The spaced-apartguide tubes 200 and the bottom surface 1118 of the planar top member1110 define a receiving region 1150 sized to accommodate the alignmentsubstrate 510 of the ferrule assembly 500. FIG. 33A shows adhesivematerial 550 applied to a portion of the top surface 516 of thealignment substrate 510 of the alignment ferrule assembly 500. Note thatthe planar top member 1110 of the alignment assembly 104P of FIG. 33A isthe counterpart to the planar top member 130 of the alignment assembly104P of FIG. 4B.

The alignment assembly 104P is combined with the alignment ferruleassembly 500 to form a plug connector 100P by inserting the alignmentsubstrate 510 into the receiving region 1150 so that the adhesivematerial 550 contacts the bottom surface 1118 of the planar top member1110. The alignment ferrule assembly 500 is then aligned relative to thealignment assembly 1110. In an example, this alignment is a six-axisalignment. Once alignment is established, the adhesive material 550 iscured, e.g., by exposure to UV light through the planar top member 1110.In an example, the adhesive material 550 has a thickness in the rangebetween 1 μm and 40 μm after alignment and curing. FIG. 33B shows theresulting plug connector 100P.

FIG. 34A is a side view of the example alignment ferrule assembly 500similar to that of FIG. 11D but having an alignment substrate 510wherein the top surface 516 is angled relative to the bottom surface518. FIG. 34A also shows the alignment assembly 104P residing above thealignment ferrule assembly 500 while FIG. 34B shows the resulting plugconnector 100P in which the guide pins 1140 define the connection angleφ relative to bottom surface 518 of the alignment substrate 510. Notethat the connection angle φ=0 corresponds to the horizontal.

PLC with Receptacle Assembly

FIG. 35A is a side view of the plug connector 100P in position relativeto the PLC 600, i.e., adjacent the front end 612 of the PLC substrate610. The PLC 600 includes a receptacle assembly 104R that in an examplehas the same construction as the alignment assembly 1200P but withoutthe guide pins 1400. The receptacle assembly 104R is disposed on the topsurface 616 of the PLC substrate 610 and oriented at the connectingangle φ so that the bore axes AB align with the guide pins 1140. Thiscan be accomplished by forming a flat section 1138 on each of the guidetubes 200 of the receptacle assembly 104R. In an example, the receptacleassembly 104R is secured to the top surface 616 of the PLC substrate 610using the adhesive material 550.

The alignment assembly 1200P is mating engaged with the receptacleassembly 104R to form the evanescent optical coupler 900, as shown inFIG. 35B. The evanescent optical coupler 900 is formed by bringing thealignment assembly 1200P and receptacle assembly 104R together along theconnecting angle φ so that the guide pins 1140 of the alignment assembly1200P slide into the bores 1136 of the receptacle assembly 104R. Whenthe guide pins 1140 of the alignment assembly 1200P are fully insertedinto the bores 1136 of the receptacle assembly 104R, the fibers 10 ofthe alignment ferrule assembly 500 of the alignment assembly are alignedwith and are in close contact with the PLC waveguides 640 of the PLC 600in the evanescent coupling region ECR.

FIGS. 36A and 36B are top elevated views of the plug connector 100P andthe receptacle connector 100R, illustrating the formation of the exampleevanescent optical coupler 900 by matingly engaging the plug andreceptacle connectors.

While the embodiments disclosed herein have been set forth for thepurpose of illustration, the foregoing description should not be deemedto be a limitation on the scope of the disclosure or the appendedclaims. It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the claims.

It will be understood by one having ordinary skill in the art thatconstruction of the described disclosure and other components is notlimited to any specific material. Other exemplary embodiments of thedisclosure disclosed herein may be formed from a wide variety ofmaterials, unless described otherwise herein.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit, unlessthe context clearly dictates otherwise between the upper and lower limitof that range, and any other stated or intervening value in that statedrange, is encompassed within the disclosure. The upper and lower limitsof these smaller ranges may independently be included in the smallerranges, and are also encompassed within the disclosure, subject to anyspecifically excluded limit in the stated range. Where the stated rangeincludes one or both of the limits, ranges excluding either or both ofthose included limits are also included in the disclosure.

For purposes of this disclosure, the term “coupled” (in all of itsforms: couple, coupling, coupled, etc.) generally means the joining oftwo components (optical, electrical or mechanical) directly orindirectly to one another. Such joining may be stationary in nature ormovable in nature. Such joining may be achieved with the two components(optical, electrical or mechanical) and any additional intermediatemembers being integrally formed as a single unitary body with oneanother or with the two components. Such joining may be permanent innature, or may be removable or releasable in nature, unless otherwisestated. It will be apparent to those skilled in the art that variousmodifications and variations can be made without departing from thespirit or scope of the claims.

For the purposes of describing and defining the present teachings, it isnoted that the terms “substantially” and “approximately” and “about” areutilized herein to represent the inherent degree of uncertainty that maybe attributed to any quantitative comparison, value, measurement, orother representation. The terms “substantially” and “approximately” and“about” are also utilized herein to represent the degree by which aquantitative representation may vary from a stated reference withoutresulting in a change in the basic function of the subject matter atissue.

It is to be understood that variations and modifications can be made onthe aforementioned embodiments without departing from the concepts ofthe present disclosure, and further it is to be understood that suchconcepts are intended to be covered by the following claims unless theseclaims by their language expressly state otherwise.

What is claimed is:
 1. An optical interconnection device forestablishing evanescent optical coupling between an array of opticalwaveguides and an array of optical fibers, comprising: a planarlightwave circuit (PLC) having a surface and that supports the array ofoptical waveguides, wherein the array has first and second sides; anadapter having an interior, spaced apart first and second tabs andspaced apart first and second arms each having a first guide feature,wherein the first and second tabs of the adapter are attached to thesurface of the PLC adjacent and outboard of the first and second sidesof the array of waveguides; a stop fixture comprising a recess with aninside edge, the stop fixture attached to the surface of the PLC andwithin the interior of the adapter and relative to the optical waveguidearray, with the recess defining an alignment surface.
 2. The opticalinterconnection device according to claim 1, wherein the recesscomprises a front-end section having a V-shape.
 3. The opticalinterconnection device according to claim 1, wherein stop fixture has aplanar top side and the inside edge makes an obtuse angle relative tothe planar top side.
 4. The optical interconnection device according toclaim 1, wherein each first guide feature comprises a slot defined byupper and lower tines of each of the first and second arms.
 5. Theoptical interconnection device according to claim 1, wherein the stopfixture comprises one or more resilient gripper elements.
 6. Anevanescent optical coupler, comprising: the optical interconnectiondevice according to claim 1 as a first optical interconnection device; asecond optical interconnection device comprising: an alignment ferruleassembly comprising an alignment substrate having a substrate centralaxis and that supports an array of optical fibers; an alignment assemblythat operably supports the alignment ferrule assembly; and wherein theadapter is configured to matingly engage with the alignment assembly ofthe second optical interconnection device to place the optical fibersand the optical waveguides in evanescent optical communication.
 7. Theevanescent optical coupler according to claim 6, wherein the alignmentassembly comprises second guide features configured to operably engagewith the first guide features of the alignment assembly.
 8. Theevanescent optical coupler according to claim 6, wherein the first andsecond guide features define a connection angle ϕ>0 relative to thesubstrate central axis of the alignment substrate.
 9. The evanescentoptical coupler according to claim 6, wherein the alignment substratehas a front-end section that is received within the recess of the stopfixture when the first and second optical interconnection devices arematingly engaged.
 10. The evanescent optical coupler according to claim9, wherein the alignment ferrule assembly is attached to a spring-loadedcarrier member, and wherein the adapter comprises a tongue thatmechanically engages the carrier member and applies a pressing forcethat presses the alignment ferrule assembly against the PLC so that theoptical fibers press against the optical waveguides when the first andsecond optical interconnection devices are matingly engaged.
 11. Theevanescent optical coupler according to claim 10, wherein the stopfixture has a planar top side, and wherein the inside edge is angledother than perpendicular to the planar top side, and wherein thealignment substrate has an angled outside edge that allows eitherface-to-face contact or line contact between the outside edge ofalignment substrate and the inside edge of the recess of the stopfixture.
 12. The evanescent optical coupler according to claim 11,wherein the stop fixture comprises one or more resilient gripperelements configured to define an interference fit between the front-endsection of the alignment substrate and the recess of the stop fixture.13. The evanescent optical coupler according to claim 12, wherein thealignment ferrule assembly comprises a latch that is movable over firstand second arms of the adapter to secure the alignment assembly to theadapter.
 14. The evanescent optical coupler according to claim 9,wherein the alignment substrate has an outer edge that comprises one ormore alignment bumps configured to align the optical fibers with the PLCwaveguides for evanescent coupling when the one or more alignment bumpsare in contact with the stop fixture.